There is an excellent mp3 lecture at the Trinity Foundation website on The Failure of Secular Economic Policy. It was given by Dr. Ronald L. Cooper, a formally trained economist and mathematician, and former faculty member at Biola University. In it he describes his Ph.D. thesis at UC Berkeley, a massive undertaking where he tested all of the macro-econometric models of the US economy, and constructed a test for each model to see how well they would predict and if they were structurally stable over time. The conclusion of his study was that all of the models were unstable and would not predict better than simple mechanical forecasting schemes. His lecture, along with the rest in the collection on the website, are a great listen for anyone interested in economics.